Sanitizers and disinfectants are formulations intended to reduce or destroy pathogenic bacteria, fungi and viruses. Quaternary ammonium compounds serve as the active antimicrobial agent in the majority of sanitizers currently used in Industrial and Institutional (I&I) applications. In addition to an antimicrobial agent, most contain co-surfactants to assist in solubilizing soil particulates, as well as chelating agents to overcome deficiencies with hard water, and builders or acids to aid in cleaning performance.
A specialized category of sanitizers and disinfectants is directed towards clean-in-place (CIP) applications. Examples of CIP applications include cleaning of dairy and brewery tanks and meat packing plants and parts. Unlike typical hard surface cleaning where high, stable foaming formulations are used, CIP applications normally demand low, fast breaking foams to avoid overflow, product loss, pump cavitation, and streaks and films on treated surfaces after drying.
Low foam sanitizing solutions are also needed for machine-applied disinfectant/cleaners. Maintenance workers use modern formulations that combine antimicrobials with surfactants to both clean and disinfect in one step. When the formulations are applied by machine, however, there is often excessive foam generation due to the high turbulence at the brush/floor interface. The resulting higher foam can lead to streaks when the floor dries and leave unsightly residue in heavily trafficked areas.
Two types of quaternary ammonium compounds are typically used to impart antimicrobial activity to household and I&I formulations. These are alkyldimethylbenzylammonium chlorides (ADBACs) and dialkyldimethylammonium chlorides (DDACs). Both of these classes of compounds are excellent surface active agents; however, the high, stable foams they develop are disadvantageous in CIP applications.
A possible solution to this problem is to include low-foaming co-surfactants in the formulations. The foam building properties of ADBACs and DDACs, however, are so potent as to overcome the normally low foaming characteristics of such co-surfactants.
A limiting consideration in the search for an appropriate co-surfactant is that many standard surfactants such as anionic sulfates, ether sulfates, or sulfonates cannot be used in quaternary ammonium-based formulations, since they form precipitates and produce hazy, two phase systems with reduced antimicrobial efficacy. Thus, co-surfactants in these formulations are normally limited to nonionics.
Another goal in using surfactants in sanitizer formulations is to reduce the surface tension of the water in the cleaning vessel, thereby improving wetting, enhancing dirt and soil removal and improving drainage of the cleaning solution. Unfortunately, most surfactants that a) are compatible with quaternary ammonium-based compounds, and, b) display low foam characteristics, have limited surface tension reduction properties at the levels employed.
One approach to reducing the foaming tendencies of disinfectant and cleaner solutions is to include silicone in the formulations. Silicones, however, tend to accumulate on surfaces, leaving residues on vessel walls and pipe linings that often become problematic in later processing stages as well as in coating and painting steps. Also, silicones are not readily biodegradable and accumulate in the biosphere, leading many CIP formulators to reject them out of hand.
Therefore, there is a need in the art for formulations that are effective in disinfecting and cleansing and possess foaming properties compatible with CIP and machine-cleaning applications. U.S. Pat. No. 4,938,893 (hereinafter the "'893 patent") discloses C.sub.1 -.sub.4 alkyl-di C.sub.6 -.sub.20 alkyl amine oxide compounds that are used in combination with a hardness sequestering agent, a source of alkalinity, and an anionic surfactant, to produce a detersive solution with low-foaming properties. Nevertheless, the formulations of the '893 patent produce too much foam for CIP and machine-applied cleaning applications. In addition, this invention is restricted to detersive applications which do not present the difficulties presented by sanitizer systems.